326 



COMPARATIVE ZOOLOGY. 



veloped the primary, secondary, and tertiary feathers of 

 the wing. The hind-limbs are formed for progression 

 walking, hopping, running, paddling, and also for perch- 

 ing and grasping. The modifications are more numerous 

 and important than those of the bill, wing, or tail. There 

 are twenty bones ordinarily, of which the tibia is the prin- 

 cipal ; but the most characteristic is the tarso-metatarsus, 



which is a fusion of 

 the lower part of the 

 tarsus with the meta- 

 tarsus. The rest of the 

 tarsus is fused with 

 the tibia. The thigh 

 is so short that the 

 knee is never seen out- 

 side of the plumage ; 

 the first joint visible 

 is the heel. 167 Most 

 Birds have four toes 

 (the external or " lit- 



tie" tO6 is always 



trt *.: nrv \ . TT V, 



bill; the meeting-line between the two raandi- Wanting) , many have 



bles is the commissure; the ridge on the upper f]irpp f! 10 hnIJiiw nr 



mandible is called culmeii; that of the lower, l 66 ' t liUX ^ C 



gonys; the space between the base of the upper "bi "" toe beinfif ab- 

 mandible and the eye is the lore ; i, forehead ; k, ' 



crown; I, scapular feathers; m, back; n, meta- SCllt j while the Os- 



tarsus, often called tarsus or tarso-metatarsus; , i i v 



o, abdomen; p, rump; g, upper tail-coverts; r, tncn has at tWO, an- 



lower tail-coverts. SWCHIlg to the third 



and fourth. The normal number of phalanges, reckoning 

 from the hallux, is 2, 3, 4, 5. The toes always end in 

 claws. 



Birds have neither lips nor teeth, epiglottis nor dia- 

 phragm. The teeth are wanting, because a heavy masti- 

 cating apparatus in the head would be unsuitable for 

 flight. The beak, crop, and gizzard vary with the food. 

 It is a peculiarity of all Birds, though not confined to 



kg f e d c b a 



FIG. 304. Principal Parts of a Bird: , primaries; 

 b, secondaries ; c, spurious wing ; d, wing-coverts ; 

 , tertiaries; /, throat, or jugulum; g, chin; h, 



